The present invention pertains to a sewing machine with a housing having an arm and a head, with a presser foot mechanism, comprising a pressure bar and a presser foot, and with a linear motor as an adjusting element for the presser foot mechanism, wherein a spring is arranged between the drive bar of the linear motor and the pressure bar.
Two exemplary embodiments of a presser foot mechanism, in which a spring acting as a low-weight coupling element is arranged between the drive bar of the linear motor and the pressure bar, are disclosed in DE 199 45 443 A1. In a first exemplary embodiment, the linear motor is arranged vertically above the pressure bar and the spring is designed as a coil spring. Due to the relatively large dimensions of the linear motor in terms of its diameter and its length, it could not be arranged within but only outside the housing head. However, this would compromise not only the handling of the sewing machine, but also its appearance.
In a second exemplary embodiment, the linear motor is arranged at a laterally spaced location from the pressure bar and the spring is designed as a leaf spring bridging over the distance between the drive bar and the pressure bar. Even though it appears to be more possible in this design to accommodate the linear motor within the machine housing, the drive bar and the pressure bar and their mounts are, however, subject to strong jamming forces and increased wear because strong horizontal force components also occur besides the vertically directed forces in the case of such an arrangement of a leaf spring.
The basic object of the present invention is therefore to provide a presser foot mechanism to be operated with a linear motor, which can be accommodated together with the linear motor at least extensively within the machine housing and operates with low wear.
According to the invention, a sewing machine is provided with a housing having an arm and a head, with a presser foot mechanism or means. The presser foot mechanism comprises a pressure bar and a presser foot. A linear motor is provided as an adjusting element for the presser foot mechanism. A spring is arranged between the drive bar of the linear motor and the pressure bar. The linear motor is arranged at least partially in the arm and its drive bar is connected via an angle lever to a spring bracket holding the spring. The spring bracket is connected to the pressure bar.
Due to the arrangement of an angle lever and the measure of mounting the spring in a bracket, which is connected to the angle lever, on the one hand, and to the pressure bar, on the other hand, the linear motor can be accommodated at least partially within the housing arm, so that it does not compromise the handling of the sewing machine and is, moreover, extensively protected from damage.
The connection between the drive bar and one arm of the angle lever as well as between the other arm of the angle lever and the spring bracket can be designed as an elongated hole-and-pin connection according or it can be brought about by a connecting rod.
The design of the spring bracket as comprising an upper holding piece associated with the angle lever and a lower holding piece associated with the pressure bar and that the two holding pieces are connected to one another by a screw, wherein the spring arranged between the two holding pieces is pretensioned leads to a detachable connection between the angle lever and the pressure bar. In the variant wherein the linear motor, the angle lever and the upper holding piece of the spring bracket are arranged together on a carrier plate detachably fastened on or in the arm, it makes it possible to connect the linear motor designed as a built-in assembly unit together with the angle lever to the pressure bar in terms of drive after the mounting in the machine housing by inserting the screw.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.